Metal oxide semiconductor (MOS) transistors find wide-ranging use in electronic devices, such as microprocessors, microcontrollers, and application-specific integrated circuits. MOS transistors generally include a gate electrode formed above a semiconductor substrate, with the gate electrode being insulated from the semiconductor substrate by a thin layer of gate insulator material (i.e., a gate dielectric). A source and a drain are spaced apart regions of either N-type or P-type semiconductor material and are generally embedded within the semiconductor substrate adjacent to the gate electrode on either side thereof. A region in the semiconductor substrate between the source and the drain, and beneath the gate electrode, forms a channel of the MOS transistor.
For years, silicon has been a conventional semiconductor material for use as the channel of a MOS transistor. However, as transistor size decreases, it is increasingly desirable for channel materials to have improved carrier mobility. Two materials with improved carrier mobility relative to relaxed silicon are germanium (Ge) and silicon germanium (SiGe) with a high germanium content. Compound gate insulators that include a dielectric layer of germanium oxide (GeOx) or silicon germanium oxide (SiGeOx), and a layer of a high k-dielectric material, such as hafnium dioxide (HfO2) have been suggested for use with these materials. Unfortunately, devices of this configuration suffer from instability arising from Ge diffusion into the HfO2 layer, and O diffusion into the Ge or SeGe layer, both of which increase gate leakage and lead to premature device failure.
Accordingly, it is desirable to provide novel semiconductor devices with a barrier layer to diminish Ge and O diffusion. It is also desirable to provide processes for preparing such devices. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.